WASHINGTON - A dispute over budget cuts that threaten dozens of smaller control towers with closure slowed Senate progress Tuesday on legislation to avoid a government shutdown on March 27.

Sen. Jerry Moran, R-Kan., refused repeatedly to permit final passage of the measure unless Democrats first allow a vote on his plan for erasing most of the cuts aimed at towers operated by Federal Aviation Administration contract employees.

Senate Majority Leader Harry Reid, D-Nev., just as persistently declined to give in, and other Democrats noted that House Republicans had rejected calls to give all federal agencies the type of budget flexibility that Moran was seeking.

The test of wills endured as Republicans and Democrats in Congress struggled with two goals - ensuring there is no interruption of routine government funding while simultaneously vying for political advantage in the wake of $85 billion in across-the-board spending cuts that kicked in earlier this month.

Across the Capitol, the Republican-controlled House began debate on a budget that promises to eliminate federal deficits in decade. The blueprint, authored by Rep. Paul Ryan, D-Wis., calls for $6.4 trillion in spending cuts and no tax increases, and is expected to clear by week's end.

For their part, Senate Republicans kept their distance from the plan, deciding not to seek a symbolic vote on it when the Senate begins its own budget debate later in the week.

Sensing an opportunity for political mischief, Senate Democrats vowed not to let Republicans off easy. They said they would require a vote on Ryan's budget - even though they unanimously oppose it.

As gridlock gripped the Senate, the top U.S. commander in South America told Congress the cuts would reduce if not eliminate the entire fleet of ships used to counter drug-runners.

Gen. John Kelly said that U.S. forces seized 150 to 200 tons of cocaine last year. If the budget cuts stand, "next year all of that will make its way ashore and into the United States," he told the Senate Armed Services Committee.

In the Senate, Moran said, "It's not my nature to be an obstructionist" as he pressed his case. He added that his proposal has support from senators in both parties and that House Republican leaders have indicated the bill's final approval would not be jeopardized if the change were incorporated.

Democrats responded tartly.

"I want to restore the Head Start to 70,000 children. I want to restore 10,000 teacher jobs," countered Sen. Barbara Boxer, D-Calif., referring to the threatened impact of across-the-board cuts elsewhere in the budget.

In general, senior members of the Senate Appropriations Committee have worked harmoniously to ease the impact of the $85 billion in spending cuts on numerous agencies.

As drafted, the measure includes House-passed provisions to give the Pentagon and the Department of Veterans Affairs flexibility in coping with the cuts. It also extends similar leeway to the departments of Agriculture, Commerce, Justice and Homeland Security, as well as the Food and Drug Administration.

There was no such provision for the FAA, where Moran said officials had ordered a 75 percent cut in funding for airport towers operated by contract employees even though the agency's overall reduction is 5 percent.

The Kansan suggested strongly that Democrats were playing politics with the issue.

"I've been trying to fathom why would the Department of Transportation, in a sense, single out this program," he said on Monday night.

"It's hard for me to fathom a good answer to that question, and the closest I can come is there are those in Washington, D.C., who want to demonstrate that we can't cut a dime - we can't cut $85 billion in federal spending from $3.6 trillion, just 28 days of spending - at all," added Moran, who doubles as chairman of the Senate Republican campaign committee.

In the case of the FAA, Moran's office circulated a list of 173 facilities that could be closed. Seven were in the senator's home state and the rest scattered around the country. Most if not all are smaller or medium-size locations.

Moran's proposal calls for transferring $50 million to the contract tower program from FAA accounts that have unspent funds. His office said the shift would leave the contract tower program with the same 5 percent cut that other parts of the agency must absorb.

FAA Administrator Michael P. Huerta told Congress recently that when it came to deciding where to cut, the agency tried to "minimize inconvenience for the maximum of travelers."

The two political parties have sought for weeks to avoid blame for any public inconvenience that results from the budget cuts, known in Washington-speak as a sequester, and it's likely they will accelerate their efforts as the cuts begin to bite.

So far, much of the back and forth has focused on relatively minor matters, including the decision to cancel White House tours and House Speaker John Boehner's periodic reminders to the public that the Capitol is open as usual for out-of-towners to visit.